Magnetic oxides, their composites and nanoparticles are uniquely suited for a wide variety of applications in new technologies, including device miniaturization, power efficiency improvement and health sector innovations. The interest in these materials is due to such properties as high resistivity, low dielectric and magnetic losses, good corrosion resistance and favorable mechanical characteristics. The book focuses on the relevant basic concepts, as well as on synthesis routes and important applications of spinel ferrites, hexaferrites and magnetic oxide nanomaterials.